Method of cementing soles to shoes



Oct. 9, 1962 s. SNITZER 3,056,984

METHOD OF CEMENTING SOLES TO SHOES Filed Jan. 6, 1.961

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BY Emu my, wal/ jaw/1M! ATTORNEYS 3,056,984 METHOD OF CEMENTING SOLES T SHOES Saul Snitzer, Worcester, Mass. B-W Footwear Co. Inc., Webster, Mass.) Filed Jan. 6, 1961, Ser. No. 81,015 Claims. (Cl. 12-142) This invention relates to the art of shoemaking and more particularly comprises a new and improved method of cementing soles to uppers.

In shoe factories today it is common practice in the assembling operations to transport shoes from operator to operator on racks holding one or more case lots. Each operator completes his operation on all of the shoes in a rack before wheeling the rack to the operator who performs the next step in assembling the shoes. This practice is commonly followed in both the lasting and bottoming operations. In this common practice, intentional delays are incorporated into the assembling sequence to allow certain things to occur. For example, after the operator applying cement for sole attaching completes this step on all of the shoes in a rack, the rack is set aside for several hours to allow the cement to set and dry. While the time required for the cement to set and dry varies with different upper stock, even with shoe uppers of a stock most conducive to setting and drying of the cement, approximately two hours are required for this result to be effected unless setting and drying is artificially accelerated.

Recently, efforts have been made to employ rink systems in the manufacture of shoes, particularly for the bottoming operations, wherein the shoes are processed on an individual basis and are passed from one operator to the next immediately upon the completion of a particular step in the manufacturing process. By employing the rink system, manufacturers hope to reduce the number of shoes in process and thereby reduce the number of lasts required for a given factory output. It will be recognized that lasts constitute one of the major capital investments in the operation of a shoe factory.

The successful operation of a rink system depends at least in part on the elimination of long periods during which time no function is performed on the shoes. Thus, for a rink system to operate successfully it is obviously necessary to eliminate the ordinarily long period required to condition the cement. Some means must be employed to accelerate the natural setting and drying process.

The primary object of my invention is to provide a process wherein the setting and drying of the cement is markedly accelerated. Several direct advantages fiow from the acceleration of cement setting and drying. First, if the setting and drying occurs in a very short period of time, a rink system may be employed most successfully in the bottoming operations.

A normal outgrowth of the rink system is the use of conveyors for transporting the shoes from operator to operator. The conveyor may also be used to carry shoes through certain locations where conditions are established that accelerate the conditioning of the cement. It is obvious that the more rapid the conditioning of the cement, the shorter and less expensive the conveyor required.

To accomplish the primary and other objects of my invention, I subject the cement applied to the upper to a series of different conditions in rapid sequence. Preferably, the cement is preheated and applied to the shoe at a temperature of approximately 110 F. After the cement coating is applied to the overlasted margin of the upper, it is permitted to cool at room temperature for approximately two minutes during which time the solvents at the surface of the coating evaporate. This slow cooling avoids the formation of a film on the surface which would retard the dispersion of the solvents. Thereafter,

the upper is passed through a heating chamber wherein the temperature is maintained at approximately 160 F. The upper remains in that chamber for approximately one minute. While in this heater the evaporation of the solvents is accelerated as the solvents are drawn from the interior of the cement coating. I theorize that more important than the actual temperature reached by the cement is the change in temperature experienced by the cement from the air cooling and drying step to the heating step. Upon leaving the heater, the upper is directed through a force cooling chamber. The air in the cooling chamber is circulated by fans or blowers which serve to carry away the vapor barrier formed about the upper by the evaporated solvents, which would inhibit further evaporation. The forced cooling of the cement coating is continued for a period of approximately one minute at a temperature of about 60 F. Thereafter, the uppers are passed through a reheating chamber which serves to reactivate the cement. The reheating chamber has a temperature of approximately F. and the shoes remain in that chamber for approximately forty seconds. During that time the cement becomes tacky and acquires maximum bond strength.

The preheating of the cement before its application to the upper has several advantages. Not only does the preheating accelerate the evaporation of the solvents but in addition more uniform flow of the cement is obtained from the cement applicator, and stripping and puddling are avoided. The viscosity of cold cement is lower than that of heated cement and, therefore, cold cement is more diflicult to control. When the viscosity of the cement is somewhat elevated, more uniform application is possible.

These and other objects and features of my invention will be better understood and appreciated from the following detailed description read in connection with the accompanying drawing, wherein:

FIGURE 1 is a box diagram representing the sequence of steps in the shoemaking process of my invention; and

FIGURE 2 is a diagrammatic view of a conveyor assembly about which the various shoemaking steps of my invention may be practiced.

In FIGURE 1 the sequence of steps followed in attaching the sole to the upper are represented separately in box form. It will be appreciated that the steps of my invention take place after the normal lasting operations are completed and are in no Way dependent upon the particular method of lasting employed. The first operator employed in the practice of my invention takes a prelasted upper and applies a heated coating of cement to its overlasted margin, as suggested in box 10. Thereafter, the several steps as represented by boxes 12, 14, 16 and 18 are conducted automatically without the attention of an operator to condition the cement coating. The first of these automatic steps is the air drying of the cement for approximately two minutes. During this period the cement is permitted to respond to room temperature and cool. After a short period of air drying, the uppers and more particularly their cement coating are exposed to a high heat zone of approximately F. for about one minute during which time the cement coatings experience a marked change in temperature. Thereafter, a forced draft is directed across the uppers to remove the vapor barrier surrounding the shoes. The shoes may be exposed to the forced draft for a period of approximately one minute. The last automatic step performed in the process is the reheating of the cement coating to reactivate it. The reheating is done at a temperature slightly in excess of normal room temperature, i.e., approximately 85 F., and occurs for a period of approximately forty seconds. After the cement is activated by the reheating, the sole is applied as indicated by box 20, by a second operator in the system. The sole may or may not be precoated with cement, and if precoated may be reactivated by a separate heater or otherwise brought to a tacky state. The particular system followed in the treatment of the sole will be determined by the sole material and the nature of the upper stock. Regardless of the condition chosen for the sole, it is placed on the bottom of the lasted upper and the parts are subjected to pressure to effect a maximum bond in the ordinary manner.

Having described briefly the several steps of my invention, I will now describe each of the steps in greater detail referring to the diagrammatic view of a conveyor and ancillary equipment shown in FIGURE 2. At the same time, specific times and temperatures will be identified as employed in an actual model of my invention. In FIG- URE 2 a tube 22 is shown surrounded by a heating coil 24, which carries cement to nozzle 26. The cement may be any heat conditionable adhesive, such as a thermoplastic or thermosetting cement. Such thermoplastic adhesives as Hycar cement and neoprene are typical examples of the cements employed. A distinct advantage is derived from heating the cement in the tube 22 as opposed to heating it in an open container (not shown) or at the nozzle 26. When the cement is heated in an open container many of the solvents contained in the cement are driven off and, therefore, the chemical formulation of the cement is changed and the cement is no longer in the condition intended by the manufacturer at the time of application. The limited physical size of the nozzle 26 does not allow adequate heat to be introduced into the cement to elevate its temperature to the degree desired. Experiments have indicated that the best results are obtained when the cement is applied at a temperature of approximately 110 F. The coil 24 may cover a length of approximately two feet on the feed tube 22 and this distance is adequate to facilitate the introduction of the heat necessary to elevate the cement to that temperature.

I suggest at 28 a lasted shoe upper upon which the heated cement is being applied to the overlasted margin. After the cement is so applied, the operator places the last bearing the shoe on a pin 30 carried by the conveyor 32 travelling in the direction indicated by the arrows 34. The two pulleys 36 and 38 describe the course followed by the conveyor 32 and it is to be understood that one or both of the two pulleys 36 and 38 may provide the drive for the system. The lasted upper coated with cement .on the overlasted margin is suggested at 28' in the position in which it is installed on the conveyor by the cementer. The conveyor carries the lasted upper exposed to room conditions in the direction of tunnel 40 surrounding a major portion of the upper run of the conveyor. In the test model 102 seconds are required for the upper to travel from the location shown at 28' to the mouth 42 of tunnel 40. During that time, the cement is air dried and the solvents particularly lying at the surface of the cement coating are allowed to evaporate. As the uppers are unencumbered by shrouds, hoods or tunnels etc., the solvents which dissipate from the cement move away from the shoes and do not form a saturated atmosphere to inhibit further evaporation of the solvents. After air drying, the uppers coated with cement enter the tunnel 4t and are subjected to the heater 44 which creates a temperature of approximately 160 F. in its zone of the tunnel. The elevated temperature at that location causes a rapid change in the temperature of the cement coating and the solvents lying deeper in the coating below the surface are caused to evaporate. However, if the uppers had not been given an opportunity to cool at room temperature preceding entry into the tunnel 40, a film may have formed over the surface of the cement which would impair further evaporation of the solvents and make it particularly difficult to drive the solvents from the cement. To draw the solvents through the film would require more than the 78 seconds of high heat found adequate in the practice of my process.

The conditioning of the cement is continued by passing the lasted uppers bearing the cement coating through a zone of rapidly moving cool air lying intermediate the ends of the tunnel 40 and created by the fans 46. The fans 46 serve not only to cool the area but in addition serve to carry away the vapor barrier which forms about each of the uppers as the solvents evaporate. In effect, the fans create a porous or absorbent atmosphere about the cement coatings to accelerate the setting and drying of the cement. In the testing of my invention, a sixty second interval was adequate substantially to complete the setting and drying of the cement.

To complete the conditioning of the cement for sole laying, it is only necessary to subject the cement once again to heat. This is accomplished by heaters 48 lying at the end of the tunnel 40, which create a warm atmosphere for the uppers. This atmosphere at a temperature of approximately F. in forty seconds reactivated the cement during testing so that it was in the proper condition for sole laying. When the shoe uppers leave the tunnel 44) at the exit 50, an operator stationed adjacent pulley 38 removes the uppers from the conveyor, applies the sole and places them in a press (not shown) and actuates the press to assist in the formation of the bond between the sole and upper stock.

From the foregoing description it will be appreciated that by the practice of my method approximately four and one-half minutes after the cement is applied to the overlasted margin the sole may be attached to the upper. The sequence of steps recited uniformly produce a quality product with many benefits to the manufacturer. The elimination of the use of racks in good part does away with the need of cleaning of the shoes, as the shoes no longer remain on the racks to accumulate dirt, dust etc. The number of lasts required in the manufacture of shoes is minimized and better production control is provided. In the very limited time required for sole laying, proper cement conditioning is effected and thus a better bond is achieved between the sole and the upper. While quartz heaters perform very satisfactorily for the application of high heat at the inlet end of the tunnel 40 and infrared lamps are most satisfactory in supplying the reactivating heat for the cement, any type of heat source may be used and thus equipment costs are not prohibitive.

While I have described in detail a preferred embodiment of my invention, I do not intend to limit the scope of my invention to the single embodiment illustrated and described as various modifications may be made of it without departing from the spirit of my invention. It is intended that the breadth of this invention be determined by the appended claims and their equivalents.

What I claim is:

1. A method of sole laying comprising the steps of providing a lasted upper and a sole, applying a heated coating of cement to the overlasted margin of the upper, air drying the cement on the margin for approximately two minutes, subjecting the cement coating to a heat of approximately F. for approximately one minute, thereafter force cooling the coating of cement by directing cooled air over its surface for approximately one minute, next subjecting the cement coating to a heat of approximately 85 F. for approximately forty seconds, and thereafter pressing the sole on the overlasted margin to bond the sole and upper together.

2. A method of sole laying comprising the steps of providing a lasted upper and a sole, applying cement to the overlasted margin, heating the coating by subjecting it to a temperature of 160 F. for approximately one minute, then directing a forced draft of cool air at a temperature of approximately 60 F. for approximately one minute over the cement, and thereafter reactivating the cement and pressing the sole on the overlasted margin to bond the sole and upper together.

3. A method of securing a sole to an upper comprising the steps of providing an upper and a sole, applying a heat activatable cement to the bottom of the upper, heating the upper for approximately one minute at a temperature of 160 F., breaking the vapor barrier on the surface of the coating by rapidly cooling the cement with moving air, and thereafter reactivating the cement coating by the application of heat and pressing the sole and upper together.

4. A method of securing a sole and an upper together comprising the steps of coating the bottom of an upper with a heat activatable adhesive carrying a heat reservoir, permitting the coating to cool at room temperature for approximately two minutes after the coating is applied, directing heat to the surface of the coating immediately after cooling to accelerate the evaporation of solvents in the cement, thereafter rapidly decreasing the temperature of the coating while evacuating the solvents in the atmosphere adjacent the surface of the coating to further accelerate the drying of the cement, and thereafter reheating the coating and pressing the sole thereon to bond the sole and upper together.

5. A method of securing a sole to an upper comprising the steps of providing a lasted upper and detached sole, applying a coating of heated cement to the overlasted margin of the upper, dissipating the surface solvents in the cement, and thereafter rapidly increasing the temperature of the coating to evaporate the solvents in the interior of the cement, directing rapidly moving cooling air over the surface of the coating to remove the vapor barrier about the cement created by the evaporating solvents, and thereafter reactivating the cement coating and pressing the sole thereon to bond the sole and upper together.

References Cited in the file of this patent UNITED STATES PATENTS 2,940,096 Bromfield June 14, 1960 

